How Long Is A Long Life? Scientists Divided Over The Outer Limits Of Human Life Span

July 6, 1986|By Robert A. Rosenblatt, Los Angeles Times

WASHINGTON — Dr. Roy Walford, thin and fit, fasts two days a week and otherwise follows a strict diet averaging just 1,500 calories a day.

Inspired by lean laboratory rats that have lived extraordinarily long and healthy lives on short rations, the University of California Los Angeles medical doctor and research scientist is firmly convinced that his regimen could help a person live to be 120 years old.

But will the Walford diet really increase longevity? ''Only if you're a rat or a mouse,'' says Dr. Edward Schneider, deputy director of the National Institute of Aging. He insists that nothing can extend the human life span -- not diet, not exercise, not vitamins.

Walford and Schneider represent opposite viewpoints in science's perpetual fascination with the possibility of prolonging life, a preoccupation that dates back at least to Ponce de Leon's futile search 450 years ago for the fountain of youth. Today's explorers, instead of combing through the wilds of southern Florida, are peering into microscopes, rearranging genes and running batteries of tests on healthy 80- and 90-year-olds.

Despite all the research, however, science and medicine have uncovered extraordinarily little about the vital subject of aging -- what it is, why it happens and whether it can be retarded.

''We all see people who we were in school with 20 years ago,'' said Dr. John Rowe, director of the Harvard Medical School's division on aging. ''Some of them look like they haven't aged at all, and others look like it's been a very tough 20 years. There must be something we can measure to show why a person is aging faster or slower. But to date we have not been able to develop that marker of aging.''

Nor do scientists know exactly why people wear out and die, although they believe that an intriguing mixture of inheritance and environment seems to determine how long they live. ''Probably half of what happens to us is genetic and the other half is in our own hands, including our lifestyle,'' said Dr. Robert Butler, chairman of the geriatrics department at Mount Sinai Medical Center in New York.

Each species seems to have a fixed life span: one month for a fruit fly, three years for a mouse, and 150 years for a giant tortoise.

''Life itself may be considered a terminal disease to which we are all committed long before birth,'' said Philip Hanawalt, chairman of the Stanford University biology department. ''The clock is probably set as soon as the fertilized egg begins to grow.''

It is a clock that man has always dreamed of cheating. ''I think we would all like to believe there's someplace in the world where the hand of time rests a little less heavy on the human brow,'' said Dr. J. Edwin Seegmiller of the University of California, San Diego's Institute for Research on Aging.

For the human species, however, the clock is apparently set at a maximum of 115 years. Methuselah notwithstanding, there is no well-documented case of a human living longer than that.

The hardy peasants in the Caucasus Mountain region of the Soviet Union were once said to live to 140 and more on a diet of yogurt. But reality proved less spectacular. Czarist Russia had a universal draft of men between 18 and 55 in World War I, and, Seegmiller said, ''there was a considerable incentive for persons to adopt the birthdates of their fathers.''

Villacabamba, a village in Ecuador, also enjoyed a vogue as a land of the long-lived -- until it was discovered that people were celebrating three or four birthdays a year. ''One old gentleman claimed to be 132, but three years before, he had reported his age as just 121,'' said Seegmiller, who accompanied an expedition there.

Until very recently, old age was a rare phenomenon.

''This is the first century of old age, the first century in which old people are mass produced,'' said Butler, who recently summoned a panoply of experts to a seminar on the biological theories of aging. A baby girl born in the United States today can expect to live 78.3 years; a baby boy, 71.1 years. For the human race merely to survive, individuals need not live much beyond the age of 30, noted Leonard Hayflick, director of the University of Florida's Institute on Aging. They must merely live to the age of sexual maturity, reproduce and then rear their young until they in turn are ready to mate.

''Why do we age, therefore, may be the wrong question,'' Hayflick said. ''The right question may be, 'Why do we live as long as we do?' ''

The answer seems related to the body's tremendous reserve capacity, its ability to flourish with just one lung or kidney, to fight off infections and repair damage from accidents. But time drains this reservoir of strength. Pneumonia, which may send a 30-year-old to bed for three days, has a 30 percent chance of killing an 85-year-old. ''The older you are,'' Walford said, ''the less it takes to finish you off.''